Welcome to the E46Fanatics forums. E46Fanatics is the premiere website for BMW 3 series owners around the world with interactive forums, a geographical enthusiast directory, photo galleries, and technical information for BMW enthusiasts.

You are currently viewing our boards as a guest which gives you limited access to view most discussions and access our other features. By joining our free community you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is fast, simple and absolutely free so please, join our community today!

If you have any problems with the registration process or your account login, please contact contact us.

First time posting, but I'm always looking. I have a 2005 bmw 325i that has the codes p0171&p0174 I've looked into this problem for several months now to find what I thought was a solution. When the codes first appeared I checked for vaccum leaked and added a fuel injector cleaner, I reset the codes every time to see how long it takes them to come back (80miles) I have cleaned the "maf sensor" and also checked the disa valve that everyone has problems with mine was perfect, took it to a Andy shop checked for vaccum leaks again and found nothing, told me might be the 02 sensors because of my loss in torque, changed 02 sensors and problem still there , so I decided to change where I go for gas,Gng to chevron now and it went three days over 300 miles with no codes, now I'm confused what the problem could be ,thought bad gas but it comes back after some days with good gas. Some help would be nice . I don't want to take it to the bmw shop unless it starts effecting the engine too much. No real bad problem a little sluggish and rough engine idle when service engine light is on

I have a 2005 325 also, I had those same code as well. Mine was due to a tear in the upper intake boot $23 part. Look at both your upper and lower intake boots, especially where it y's and you may find your issue. It may be small enough of a tear where the engine heating and cooling could be making it smaller or bigger. I did that as well as my secondary air sensor and lines but if you checked your vacuum you should just need to do your boots.

Hope it helps, and just telling you what I just did to mine with the same codes!

Alright so Tried to unplug maf sensor, the first time I unplugged it nothing happened it smoothed out (barley any difference) than I did again just to make sure ,it puttered and went all crazy. I'm not sure if that's good or not?

I checked again for vaccum leaks, still nothing I've Tried the smoke test but this time I just sprayed it with carb cleaner on cold start(still no leaks found, even got crazy with it and started spraying the hoses and boots from top to bottom). Did see some little cracks in the upper boot, real small, the width of a infants nail maybe, sprayed those hopeing for a idle change but nothing.

In my 2000 323Ci (155k miles), 2001 Xi (with 232k mi), and 2004 325i (96k mi), we have to pass a smog test every other year here in California. The 2001 and 2004 are running fine, but showing the P0171 and P0174 'lean' codes and so won't pass smog. Despite the tears and totally shot hoses throughout the motor (my son bought it that way) and a smooshed front corner, the 2000 is not throwing any codes, which makes no sense, but hallelujah.

ALL THREE had a tear in the bottom of the ribbed part of the intake tube after the MAF sensor, which is caused by lifting up the cover of the air filter over the years. It is easy to check: take off your air filter cover + MAF by loosening the adjacent hose clamp, and shine a light around the tube in a dark garage while bending it upwards. The tube is about $28 online, and the 2004's motor had a bigger tube than the other two. It is easy to replace, compared to most other BMW repairs.
BTW- Caulking and duct taping the tube's cracks doesn't work, since so much wiggling is involved to get the MAF Sensor and air filter back on.

While you are there, spray MAF Cleaner (about $5 at AutoZone) on the delicate MAF sensor inside the unit and check that the rectangular flap valve stuck into the engine behind the tube is working. A few bolts and it pops right out. It tends to get gummed up with gunk so it doesn't move easily. Just clean the gunk off with whatever is handy. I used WD-40, a flathead screwdriver to scrap the edges, and a rag.